Are these new APs? Do you have a second domain on your VWLAN? If so, check each domain for the BSAPs and make sure the licenses are installed and moved the correct domain.
To follow-up on Eric's suggestion: another thing you need to do is make sure that the APs are assigned to a template where the correct AP firmware is uploaded. You need to be running AP firmware version 2.6.2-7. Note that AP firmware correlates to the vWLAN version you are running. It is NOT backward compatible. For vWLAN v. 188.8.131.52, you need AP firmware 2.6.2-7. I noticed you said they currently are on 6.9.x...
I have marked this questions as "assumed answered".
If this is not the case or you have more questions, feel free to respond to this thread.